WASHINGTON — Gay marriage wouldn’t have passed in the Washington state Legislature this year without Gov. Chris Gregoire’s decision to reverse course and push for it. Legislators’ personal pleas to colleagues, as epitomized by Republican Rep. Maureen Walsh’s passionate floor speech about her desire to throw her daughter a wedding someday, also played a major role. The speech went viral on YouTube.

But according to the bill’s sponsor, Democratic state Sen. Ed Murray, there was nothing more crucial to the legalization of gay marriage than support from high-profile businesses such as Nike Inc. and Microsoft Corp. “It’s how we got moderate Republicans and conservative Democrats to vote for this,” he said.

Murray and others first harnessed support from the business community for gay rights in 2006 by using an economic development argument to pass an anti-discrimination bill that had been in the works for 29 years. Support from Boeing Co. and Microsoft helped turn key votes.

Since that time, gay rights activists have built aggressively from their original base of industry support. Some gay rights groups have hired lobbyists whose sole focus is reaching out to business leaders.

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Those efforts culminated in more than 100 businesses publicly supporting gay marriage in Washington state before the bill’s passage in February, from heavy-hitting corporations such as Starbucks Corp., Google Inc. and Alcoa Inc. to mom-and-pop shops scattered around the state. Small business support was key to turning individual legislators, who “know their local businesses,” Murray said.

This is not an anomaly. Support from businesses has also been important in other states that have debated gay marriage, including New York, which voted to legalize it in 2011, and Maryland, which, like Washington, legalized gay marriage in February but faces a referendum effort to put the issue before voters.

In Maine, gay marriage was legalized by the Legislature and then-Gov. John Baldacci in 2009, but was overturned later that year at the polls. At that time, supporters of gay marriage did push a pro-economy message, arguing that legalizing gay marriage would help boost tourism, in particular. Gay marriage is again on the ballot in Maine, with voters making their choice this fall.

The driving force behind business involvement has less to do with the money that gay people might spend in the state than with workforce concerns. As more states move toward legalizing gay marriage, more businesses fear being left behind in places seen as backward by gay workers and other young employees who feel strongly about the issue.

“If you’re sending a signal to the world that you’re biased, it doesn’t just scare away gay people,” said Stephen Dull, vice president for strategy and innovation at the North Carolina-based VF Corp., a Fortune 500 company. “It scares away everyone.”

North Carolina voters will consider on May 8 whether to put the state’s existing ban on gay marriage in the state constitution. If that happens, Dull says, it will be even tougher than it already is to recruit the mobile, metropolitan, high-level employees the company is looking to attract for its Greensboro headquarters. VF is the parent company to a host of high-profile fashion brands, including The North Face, Nautica, Lee and Lucy. VF has not taken a public stand in favor of gay marriage, but many of its employees have.

Dull says he already has to reassure many of his potential recruits that they wouldn’t be moving to a place that is straight out of the rural South of a generation ago. “If this were going on when I was recruited, I don’t think I could have joined,” Dull said. “It’s not that we’re trying to recruit gay talent, but people see it as a sign of how welcome their ideas will be, no matter how different. And that’s important for innovation.”

Mitchell Gold, who runs a high-end, North Carolina-based home furnishings company, says approval of the gay marriage ban might force him to overhaul his operations in order to recruit the design talent he needs. “At some point we might end up having to move our creative offices out of this state to an area where we’ll have an easier time recruiting a diverse work force,” he said.

In February, the Human Rights Campaign, which lobbies on gay issues, named Goldman Sachs CEO Lloyd Blankfein its corporate spokesperson in the campaign for same-sex marriage.

“America’s corporations learned long ago that equality is just good business, and is the right thing to do,” Blankfein said in a video. “Join me and a majority of Americans who support marriage equality.”

Blankfein’s prominent role may seem surprising because of Wall Street’s presumed conservative culture, but many financial firms have long offered competitive benefits for gay workers and their families. And in no other sector of the economy is the competition for talented workers more cutthroat.

Gay marriage opponents from the National Organization for Marriage have taken notice of this trend. In response they have launched their own effort, called the Corporate Fairness Project, to pressure businesses to stay neutral in the debate.

“I don’t believe that you can work for a company that has taken a position on this and feel that both sides are well represented,” said Jonathan Baker, director of the Corporate Fairness Project. “Both sides should be able to go to work and feel comfortable. By a company taking a corporate position on the matter, they are automatically going to make one side or the other feel a little less comfortable about it.”

Baker’s group is also working to ensure that companies don’t discriminate against employees because they oppose gay marriage, which Baker insists is happening with some regularity.

Bank of America and Cisco came under fire from the National Organization for Marriage for terminating their relationships with leadership consultant Frank Turek because of his vocal opposition to gay marriage. They both subsequently reinstated him as an eligible vendor in good standing. “As we see more and more companies jumping into the marriage debate,” Baker said, “we think it’s certainly a risk that could grow.”

The Human Rights Campaign publishes a Corporate Equality Index that evaluates companies each year based on factors ranging from their nondiscrimination policies to the strength of their benefits for gay workers. The results are used to help guide gay job searchers to places where they can expect to be treated equally and gay shoppers to companies that they should support, through an online buyer’s guide that is available as an iPhone app. The Human Rights Campaign has gained influence with private sector employers through these endeavors, and works with companies to help them adopt practices that would improve their scores.

Now the gay rights organization is leveraging that influence to persuade companies to enter the political fray. “What better next step,” said Deena Fidas, deputy director of the Human Rights Campaign’s Workforce Project, “than for these organizations to jump into the debate with a strong public face and public voice.”

The convergence of these concerns is causing interesting dilemmas for businesses in states where support for gay marriage doesn’t poll well with the general population. In North Carolina, for example, many companies have been officially staying out of the debate over the proposed constitutional amendment while lobbying hard behind the scenes.

While VF Corporation is remaining officially neutral, Dull and others on its leadership team have been quietly lobbying local business organizations to oppose the amendment. “Different corporations have different sets of values,” he said. “One of our values is politeness and respect. That could be for customers or shareholders, and for us that’s a reason for the corporation not to take a stand.”

Bank of America, which is a prominent supporter of the Human Rights Campaign and receives a 100 percent score from the Corporate Equality Index, has been walking a fine line between taking a position and remaining on the sidelines. The company has not issued a public statement against the anti-gay marriage amendment. On the other hand, in an online video released last week, senior Bank of America executive Catherine Bessant argues that passage of the amendment would be “a direct challenge to our ability to compete nationally for jobs and economic growth.”

Chris Hughes, co-founder of Facebook and now editor and publisher of The New Republic, wrote an open letter to the North Carolina General Assembly in September as it was considering whether to put the amendment on the ballot. In the letter, Hughes, who was born in North Carolina and is gay, argues that the amendment will be bad for business. Hughes helped drive Facebook “likes” for EqualityNC, the gay rights organization that is leading the campaign against the North Carolina amendment, up from 6,000 to 40,000 in a matter of weeks by pledging to donate a dollar for each “like.”